Optic fibre networks may include multiple “nodes”, which may comprise a cable junction, spare cable loops or both. For purposes of this patent specification and claims, a “node” means a portion of a cable network which consists of either a cable junction or one or more cable loops (to supply a length of cable which may be drawn on for future system expansion, repairs or the like) or both of loops and a junction. It is desirable to provide a system that permits an uncut length of cable to be inlaid from the surface without cutting. For such purpose, network components and in particular the components provided at the cable nodes must be adapted for surface inlaid installation without no or minimal need to thread a free end of the cable through any component.
Repairs and future expansion require convenient access to additional lengths of cable, which preferably may be provided by building into the system spare cable loops in order to minimize the requirement of cable splicing as the need arises for additional cable. However, cable loops can be difficult to form and keep in place during and after the system installation, as fibre optic cable is typically relatively stiff and retains a “memory” and thus often defies being formed into tight loops and holding such loops in place during burial. Another requirement in such a system is that the nodes (which may include delicate cable junction equipment) be protected against damage.
It is desirable to provide a convenient means for installing and protecting one or more cable loops and optionally a junction box. Ideally, protection is given against compression or crushing as well as moisture, while permitting quick and simple installation of the loops and/or junction box within a narrow trench. In the present inventor's previous patent application (Published Canadian Application No. 2,337,284), a rigid junction box is disclosed around which additional cable loops may be formed. An optional rigid frame is provided to hold both the junction box and up to several loops of cable. The junction box and optional frame may be buried at a system node. The present invention relates to an improved modular system for holding either cable loops or a junction box, or both, for burial as part of a fibre optic cable network. Preferably, the network is buried within a narrow, slit-like trench which may be cut into either a hard surface such as pavement or a soft surface such as turf.
A cable system installed within a soft surface such as turf is typically set into a trench which may be somewhat wider and deeper in comparison with a hard surface such as asphalt or other pavement; it is easier to dig into a soft surface and a deeper setting of the fibre optic cable is desirable to avoid crushing or distortion when, for example, equipment rolls over the surface.